GN: Allow setting the path to Python

tools/gn/docs/reference.md

 # GN Reference
 
 *This page is automatically generated from* `gn help --markdown all`.
 
 ## **\--args**: Specifies build arguments overrides.
 
 ```
   See "gn help buildargs" for an overview of how build arguments work.
 
   Most operations take a build directory. The build arguments are taken
@@ skipping 158 matching lines @@
   This is probably not useful; the use-case for this feature is
   generally executable targets.
 
   The runtime dependency file will list one file per line, with no
   escaping. The files will be relative to the root_build_dir. The first
   line of the file will be the main output file of the target itself
   (in the above example, "bar.so").
 
 
 ```
+## **\--script-executable**: Set the executable used to execute scripts.
+
+```
+  By default GN searches the PATH for Python to execute scripts in
+  action targets and exec_script calls. This flag allows the
+  specification of a specific Python executable or potentially
+  a different language interpreter.
+
+
+```
 ## **\--threads**: Specify number of worker threads.
 
 ```
   GN runs many threads to load and run build files. This can make
   debugging challenging. Or you may want to experiment with different
   values to see how it affects performance.
 
   The parameter is the number of worker threads. This does not count the
   main thread (so there are always at least two).
 
@@ skipping 485 matching lines @@
 ```
   GN optionally generates files for IDE. Possibilities for <ide options>
 
   --ide=<ide_name>
       Generate files for an IDE. Currently supported values:
       "eclipse" - Eclipse CDT settings file.
       "vs" - Visual Studio project/solution files.
              (default Visual Studio version: 2015)
       "vs2013" - Visual Studio 2013 project/solution files.
       "vs2015" - Visual Studio 2015 project/solution files.
-
-  --sln=<file_name>
-      Override default sln file name ("all"). Solution file is written
-      to the root build directory. Only for Visual Studio.
+      "xcode" - Xcode workspace/solution files.
+      "qtcreator" - QtCreator project files.
 
   --filters=<path_prefixes>
       Semicolon-separated list of label patterns used to limit the set
       of generated projects (see "gn help label_pattern"). Only
-      matching targets will be included to the solution. Only for Visual
-      Studio.
+      matching targets will be included to the solution. Only used for
+      Visual Studio and Xcode.
 
 ```
 
+### **Visual Studio Flags**
+
+```
+  --sln=<file_name>
+      Override default sln file name ("all"). Solution file is written
+      to the root build directory.
+
+```
+
+### **Xcode Flags**
+
+```
+  --workspace=<file_name>
+      Override defaut workspace file name ("all"). The workspace file
+      is written to the root build directory.
+
+  --ninja-extra-args=<string>
+      This string is passed without any quoting to the ninja invocation
+      command-line. Can be used to configure ninja flags, like "-j" if
+      using goma for example.
+
+  --root-target=<target_name>
+      Name of the target corresponding to "All" target in Xcode.
+      If unset, "All" invokes ninja without any target
+      and builds everything.
+
+```
+
+### **QtCreator Flags**
+
+```
+  --root-target=<target_name>
+      Name of the root target for which the QtCreator project will be
+      generated to contain files of it and its dependencies. If unset, 
+      the whole build graph will be omitted.
+
+
+```
+
 ### **Eclipse IDE Support**
 
 ```
   GN DOES NOT generate Eclipse CDT projects. Instead, it generates a
   settings file which can be imported into an Eclipse CDT project. The
   XML file contains a list of include paths and defines. Because GN does
   not generate a full .cproject definition, it is not possible to
   properly define includes/defines for each file individually.
   Instead, one set of includes/defines is generated for the entire
   project. This works fairly well but may still result in a few indexer
@@ skipping 663 matching lines @@
   This target can be used on all platforms though it is designed only to
   generate iOS/OS X bundle. In cross-platform projects, it is advised to
   put it behind iOS/Mac conditionals.
 
 ```
 
 ### **Variables**
 
 ```
   bundle_root_dir*, bundle_resources_dir*, bundle_executable_dir*,
-  bundle_plugins_dir*, deps, data_deps, public_deps, visibility
+  bundle_plugins_dir*, deps, data_deps, public_deps, visibility,
+  product_type
   * = required
 
 ```
 
 ### **Example**
 
 ```
   # Defines a template to create an application. On most platform, this
   # is just an alias for an "executable" target, but on iOS/OS X, it
   # builds an application bundle.
@@ skipping 29 matching lines @@
             rebase_path("$gen_path/$app_name", root_build_dir)
       }
 
       bundle_data("${app_name}_bundle_executable") {
         deps = [ ":${app_name}_generate_executable" ]
         sources = [ "$gen_path/$app_name" ]
         outputs = [ "{{bundle_executable_dir}}/$app_name" ]
       }
 
       create_bundle("${app_name}.app") {
+        product_type = "com.apple.product-type.application"
         deps = [
           ":${app_name}_bundle_executable",
           ":${app_name}_bundle_info_plist",
         ]
         if (is_ios) {
           bundle_root_dir = "${root_build_dir}/$target_name"
           bundle_resources_dir = bundle_root_dir
           bundle_executable_dir = bundle_root_dir
           bundle_plugins_dir = bundle_root_dir + "/Plugins"
         } else {
@@ skipping 3542 matching lines @@
 ```
 ## **precompiled_source**: [file name] Source file to precompile.
 
 ```
   The source file that goes along with the precompiled_header when
   using "msvc"-style precompiled headers. It will be implicitly added
   to the sources of the target. See "gn help precompiled_header".
 
 
 ```
+## **product_type**: Product type for Xcode projects.
+
+```
+  Correspond to the type of the product of a create_bundle target. Only
+  meaningful to Xcode (used as part of the Xcode project generation).
+
+  When generating Xcode project files, only create_bundle target with
+  a non-empty product_type will have a corresponding target in Xcode
+  project.
+
+
+```
 ## **public**: Declare public header files for a target.
 
 ```
   A list of files that other targets can include. These permissions are
   checked via the "check" command (see "gn help check").
 
   If no public files are declared, other targets (assuming they have
   visibility to depend on this target can include any file in the
   sources list. If this variable is defined on a target, dependent
   targets may only include files on this whitelist.
@@ skipping 957 matching lines @@
 
 **  \--args**: Specifies build arguments overrides.
 **  \--color**: Force colored output.
 **  \--dotfile**: Override the name of the ".gn" file.
 **  \--fail-on-unused-args**: Treat unused build args as fatal errors.
 **  \--markdown**: Write help output in the Markdown format.
 **  \--nocolor**: Force non-colored output.
 **  -q**: Quiet mode. Don't print output on success.
 **  \--root**: Explicitly specify source root.
 **  \--runtime-deps-list-file**: Save runtime dependencies for targets in file.
+**  \--script-executable**: Set the executable used to execute scripts.
 **  \--threads**: Specify number of worker threads.
 **  \--time**: Outputs a summary of how long everything took.
 **  \--tracelog**: Writes a Chrome-compatible trace log to the given file.
 **  -v**: Verbose logging.
 **  \--version**: Prints the GN version number and exits.
 
 ```